1. Field of the Invention
The present invention relates to a sheet original conveying apparatus in which a sheet original is conveyed to a reading position and the sheet original conveyed to the reading position reverses its travel direction and it is turned over from a front face to a rear face.
2. Related Background Art
In the past, sheet conveying apparatuses in which a sheet is conveyed and is turned over or reversed the faces thereof have been used for conveying an original in an image forming apparatus of a copying machine, and various kinds of sheet conveying apparatuses have been proposed (hereinafter, a sheet conveying apparatus used for conveying the original is referred to as "original conveying apparatus").
Now, an example of a conventional original conveying apparatus will be briefly explained.
Such an original conveying apparatus is designed so that:
(i) both-face imaged originals stacked on an original tray (sheet stacking means) are successively conveyed to an image reading position, PA1 (ii) thereafter, the original is turned over by an original reverse means and then is conveyed to the image reading position, PA1 (iii) an image on a second surface of the original is read, PA1 (iv) then, the original from the image reading position is turned over by the original reverse means and then is conveyed to the image reading position again, PA1 (v) an image on a first surface of the original is read, and PA1 (vi) the original is discharged from the image reading position.
When the above-mentioned treatments (i) to (vi) are completed regarding a single original, the treatments (i) to (vi) are repeated regarding a succeeding original, thereby reading the images on all of the both-face imaged originals.
Another original conveying apparatus is disclosed in Japanese Patent Application Laid-Open No. 4-116071.
As shown in FIG. 43A, this apparatus has an original tray (sheet stacking means) 504 on which a plurality of originals are stacked, and a platen 510 defining an original reading position is disposed below the original tray. At the right of the original tray 504, there are disposed a sheet convey means (not shown), convey paths 501, 502 and a convey path (sheet reverse means) 503 so that, after the originals stacked on the original tray 504 are separated one by one, the separated original is conveyed to the convey paths 501, 502, . . . . Further, the convey path 503 is communicated with the platen 510, and a flapper disposed at a junction between the convey paths 502 and 503 serves to switch the paths 502, 503 from one to the other. On the other hand, another convey path communicated with the original tray 504 is formed at the left of the platen 510 so that the original on the platen 510 can be returned to the original tray 504.
In this apparatus, when the sheet convey means is driven, the original stacked on the original tray are separated one by one, and the separated original is conveyed to the convey paths 501, 502. When a trail end of the original passes through the flapper 506, the flapper 506 is switched toward the convey path 503, as a result that the original is conveyed to the platen 510 in the reversed condition. When the original is rested on the platen, an image on a second surface of the original is read, and then, the original is returned to the original tray 504 through a convey path. Incidentally, the flapper 506 is returned to its initial position after the trail end of the original leaves the flapper.
Regarding a succeeding original, similar to the preceding original, after an image on a second surface of the original is read, the original is returned to the original tray 504. Further, the read image on the second surface of the original is transferred onto a transfer sheet (not shown), and the transfer sheets on which the images were formed are stacked on an intermediate tray. When the reading of the images of the second surfaces of all originals is completed, in a similar manner, the originals stacked on the original tray 504 are supplied one by one from the lowermost one, and the supplied original is turned over and then is conveyed onto the platen 510. Then, an image on a first surface of the original is read. Incidentally, the read image of the first surface is transferred onto the other surface of the corresponding transfer sheet re-supplied from the intermediate tray.
By the way, in the firstly mentioned conventional apparatus, since the original is once set at the reading position, then is returned without the reading, then is turned over, then is set on the reading position again, and then is read (image of second surface). So, it takes a long time to read the image, and, thus, very long time is required for reading all of the originals.
In the secondly mentioned apparatus, since the images on one surfaces of all originals are read and then the images on the other surfaces of all originals are read, a circulating path for circulating the originals (more specifically, convey paths 502, 503 for turning over the originals from the original tray 504 and for conveying the turned-over original onto the platen 510, and a convey path for returning the original from the platen 510 to the original tray 504) is required. Thus, the apparatus becomes complicated and expensive.